I guess in a sort of a way, it is entirely dependant on the circumstances the fish is caught, or the reason it is being weighed, if (say) it is caught during a tightly ruled comp of some sort, then very acurate weights and lengths are necessary, simply because big cash or prizes can be won or lost on a few grams, similarly, a game comp (say) requires tackle and traces and stuff to also comply to strict rules, but if it is just to tell your mates that you caught a XXX and it was 6KG, then who cares if it was weighed on the Bathroom scales, or just a wild (but educated) guess? get where I am coming from, sometimes it will make a huge difference, sometimes bugger all, one local comp run each year down my way is purely a total length of fish caught (with photos) so most target Flathead and stuff, all fish are released, (but not completely enforced, just incase someone wants a feed as well) but need to be photographed on a measure that is supplied on the day of the comp, so no one knows the colour or description of the measuring device, so cheating is pretty well a non event, and the prizes are pretty lame as well, but it attracts hordes of people to fish it! how simple is that?